Single-cam and dual-cam compound archery bows have power cams mounted on one or both ends of the bow limbs to control the draw force on the bowstring and the bending of the limbs as the bowstring is drawn. In single-cam bows, there is a power cam on the end of one bow limb, and a wheel on the end of the other bow limb to control or time take-up of a power cable at the power cam and let-out of the bowstring and control cables at the power cam as the bow is drawn. In dual-cam bows, power cams are mounted on the ends of both bow limbs, with each including groove segments to control let-out of the bowstring cable at the opposing cam. In conventional single-cam and dual-cam bows or crossbows, the power cables or cable segments are anchored near the end of one or both bow limbs, at the axles in most cases.
Briefly stated, in accordance with the presently preferred embodiments of the invention, the power cable or cable segment is anchored not to the end of a bow limb, but is trained around additional let-out means in the cam or control wheel at the end of the bow limb. This additional let-out means decreases limb movement as the power cam takes up the power cable during the power stroke, and allows the design of the power cam take-up groove to be larger and thereby facilitate use of larger radii in designing the cable path to reduce fatigue of the power cable. The additional let-out means also facilitates bow designs with increased pre-stress in the bow limbs while minimizing movement of the limbs during the power stroke, thereby reducing limb shock and increasing efficiency. This additional let-out means also facilitates additional control of the cam and/or cam wheel rotation between the upper and lower limbs because the additional cross-coupling forces the rotation to be in unison. As applied specifically to dual-cam bows and crossbows with draw stops on one or both cams, the invention permits continued rotation at both cams until the draw stops are engaged at both cams.
A compound archery bow in accordance with a first aspect of the invention includes a handle having projecting limbs. (The term “compound archery bow,” as employed in this application, encompasses both compound traditional bows (e.g., FIGS. 1–19) and compound crossbows (e.g., FIGS. 20–22A).) A first pulley is mounted for rotation around a first axis on a first of the limbs, and a second pulley is mounted for rotation around a second axis on a second of the limbs. In single-cam bows, one of the pulleys is a control wheel and the other pulley is a power cam. In dual-cam bows, the pulleys are respective power cams. A bow cable arrangement extends between the pulleys, and includes a bowstring cable extending from bowstring let-out grooves in the first and second pulleys so that, as the bowstring cable is drawn away from the handle, the bowstring cable lets out or unwraps from the bowstring grooves and rotates the pulleys around the respective axes.
First and second cables extend from cable take-up grooves on the respective pulleys to first and second cable let-out means on the respective opposite pulleys. Thus, as the bowstring cable is drawn away from the handle, the first and second cables are each taken up or wound at one end onto one of the pulleys and let out or unwound at the other end from the other pulley. The let-out means preferably comprises at least one groove from which the cable is let-out or unwrapped as the cable is drawn. This let-out groove preferably is circular and concentric with the axis of pulley rotation but can be non-circular and/or non-concentric with the axis of rotation. In some embodiments, the let-out grooves are disposed on opposite sides of the bowstring let-out groove for improved balance. The let-out means alternatively may comprise one or more posts mounted on the pulley and offset from the axis of pulley rotation.